#include <iostream>
#include <stdio.h>
using namespace std;

int main()
{

    int graph[51][51];

    int cases;
    int parts;
    int a,b;
    int base;
    int root;
    int prec;
    scanf("%d",&cases);

    int cnt=1;
    int out_i;

    while(cases > 0)
    {
        int out[1010][2];
        out_i=0;

        scanf("%d",&parts);
        for(int i=0;i<51;i++)
            for(int j=0;j<51;j++)
                graph[i][j] = 0;

        for(int k=0;k<parts;k++)
        {

            scanf("%d %d",&a,&b);

            if(k==0)
            {
                base=a;
                root=a;
            }
            graph[a][b]++;
            graph[b][a]++;
        }

        bool solvable = true;
        int counter=0;

        for(int i=0;i<51;i++)
        {
            for(int j=0;j<51;j++)
            {
                if(graph[i][j]!=0)
                {
                    counter +=graph[i][j];
                }
            }
            if(counter % 2 != 0)
                solvable = false;
        }

        /*
        for(int i=0;i<51;i++)
        {
            for(int j=0;j<51;j++)
            {
                if(graph[i][j]!=0)
                    counter ++;
            }
            if(counter == 0)
                solvable = false;
        }
        */

        printf("Case #%d\n",cnt);
        if(solvable)
        {
            for(int l=0;l<1001;l++)
            {

                for(int i=0;i<51;i++)
                {
                    while(graph[base][base]>0)
                    {
                                out[out_i][0]=base;
                                out[out_i][1]=base;
                                out_i ++;
                                //printf("%d %d\n",base, base);
                                graph[base][base] -=2;

                    }

                    if((graph[base][i])!=0)
                    {

                            //printf("%d %d\n",base,i);
                            out[out_i][0]=base;
                            out[out_i][1]=i;
                                out_i ++;

                            graph[base][i]-=1;
                            graph[i][base]-=1;
                            //prec=base;
                            base=i;


                    }

                }
            }
        }

        if(out_i  == parts)
        {

            for(int l=0;l<out_i;l++)
                printf("%d %d\n",out[l][0],out[l][1]);

            if(cases >1)
                printf("\n");
        }

        else
        {   if(cases >1)
                printf("some beads may be lost\n\n");
            else
                printf("some beads may be lost\n");
        }
        cases --;
        cnt++;
    }


    return 0;
}